Renal Disease Flashcards
What does the kidney do?
- Filter out toxins-clearance
- Make hormones
- Fluid balance
Measuring clearance:
- GFR most common-cheap biomarkers urea and creatinine
- If we want to be more accuate we use creatinine clearance
- Radioactively labelled EDTA is injected into patient and look at clearance and degradation ratio to give accurate GFR.
- Inulin is only really used in lab experiments
What influences creatinine?
GFR falls when we lose kidney function.
The creatinine only rises when we get down to 40, where it rises exponentially
When closed to dialysis it will pick up problems very quickly but not so accurate for early disease.
Urea graph is the same as this. Only has exponential change at low GFRs ie when kidney function is very low.
If want immediate result use this but for more accurate, use EDTA or creatinine clearance (but these are more laborious to do)
What influences muscle bulk?
Creatinine supplements can react with test
More muscle due to fitness will have higher creatinine
Vegetarians and vegans will have less creatinine
In dystrophy where muscle is low or amputation they will have less muscle bulk and so creatinine will be lower.
MDRD-can be generated from simple creatinine test. Age of patient and sex of patient and creatinine can give eGFR. Because it is logarithmic it transforms exponential graph into straight line
Cockcroft Gault-can’t do from labs alone, need to know the weight of the patient too
Ethnicity has been removed form the equation because not as relevant.
Creatinine value in this example isnt as accurate as you want it
Queen-short, old, female
Usain-male, afro carribean, muscular
If this was a real result she would need to be seeing a nephrologist.
Stages of kidney disease:
Only below 15 is advanced kidney disease where you are considering dialysis
AKI stages
Use serum creatinine to determine AKI stage not GFR.
Creatinine is a dynamic test so it is used to see if acute or chronic kidney disease as if creatinine is changing rapidly, probably more likely to be AKI.
How does kidney damage present?
Pyuria=white cells in urine
What laboratory or bed side tests detect renal disease?
- early urea and creatinine with electrolytes
- Urine dipstick-picks up haematuria, eg due to cancer, TCC, stone
- If ran marathon, myoglobin will be high in urine
Urine analysis
Proteinuria-need to quantify this
Protein is due to kidney damage
More than 1g significant proteinuria
more than 3g-significant nephrotic protein loss
Urine analysis-leukocytes
As urine gets concentrated it takes structure of place where it gets stuck and forms cast eg RBCs on top of each other compress to form casts.
How do patients with renal disease present clinically?
If do have abnormal tests then need to do imaging. Tend to choose Ultrasound as first scan to do.
Imaging
US can pick up if there is obstruction as dark urine accumulating in pelvis.
Stones cause acoustic shadowing
Other images
CT is there is cancer suspicion
Timeframe distinguishes the 2
AKI-looks at changes in creatinine so typically need previous creatinine level taken
3 causes of AKI:
Pre renal failure-develops in kidney due to something that happened before kidney eg reduced oxygen delivery due to low BP or hypoxia
Renal-in kidney itself, rare
Post renal-obstruction/blockage
Pre renal:
- Anaphylaxis-vasoconstriction-drop blood flow
- diarrhoea-drop blood flow
Post renal obstruction
Early US picks up blockage
Nephrostomy if blockage is higher up
Renal damage
Looking at rare syndromes
Acute kidney injury pathogenesis:
When to consider a kidney biopsy?
The pathological basis of disease:
Surgical sieve
What condition is this?
=nephritic syndrome
-Hypertension, high urea and creatinine, blood in urine, he has inflammation in his glomerulus
Nephrotic-would be swelling and low albumin and either nephritic or nephrotic need biopsy and seen by nephrologist asap.
Rapidly progressive glomerulonephritis-could be caused by good pastures syndrome or vasculitis eg SLE
Myeloma is rare
Management of CKD
Surgical sieve for CKD:
Symptoms of renal disease
What a nephrologist does:
